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Ping Situ, Trefford L Simpson, Carolyn G Begley; Test-retest repeatability and calibration of a new automated Belmonte esthesiometer. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):6080. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
We have developed a custom, automated Belmonte esthesiometer at Indiana University. The purpose of this study was to calibrate the instrument and quantify repeatability of detection thresholds measured with room temperature pneumatic stimuli.
The esthesiometer is a dual chamber mechanical, chemical (CO2) and thermal pneumatic device. There is computer control of flow, %CO2 and temperature and computerized collection of subject responses. A temperature sensing circuit provides feedback to maintain a steady stimulus temperature independent of air-flow and ambient temperature. The output pressure and temperature esthesiometer was calibrated using a flow sensor (HONEYWELL AWM3100 V) and thermocouple (OMEGA type K). 15 non-lens wearing subjects and 52 adapted lens wearers had pneumatic detection thresholds estimated using an Ascending Methods of Limits in 2 sessions with mean (± SD) interval 3.5 (± 2.1) days between sessions. Each threshold was the average of the 3 flow rates at which subjects first reported the stimulus. Data analysis was conducted using R (3.1.2).
After calibration, mean (± SD) test and retest thresholds were 58.33 (± 20.6) and 58.85 (± 23.2) ml/min respectively. The bivariate test-retest regression slope (ideal = 1.0) was 1.07 (95% CI 0.9-1.36) and the correlation coefficient of concordance was 0.74 (95% CI 0.61- 0.84). Bayesian mean test-retest difference was -0.057 (95% HDI -2.2 - 5.7 ml/min). Figure 1 shows the test-retest results and some posterior estimates of the data.
The new design provides repeatable room temperature threshold estimation. Calibration of the flow, temperature and CO2 content enable the measurement of the full range of ocular sensory processing channel capabilities.
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